Coffee: researchers were surprised by the lack of chemicals detected. Photo: sot

The first part of the study tested three food chemicals: acrylamide, aluminium and perchlorates.

While the results fell within the safe range overall, levels of acrylamide appeared to be of possible concern to human health.

Acrylamide forms naturally in carbohydrate-rich foods when they are heated at high temperatures by roasting, baking, grilling, toasting and frying.

"The acrylamide is formed in natural chemical reactions between food components that also give us tasty browning and crunchy texture," says Professor Ian Rae, an honorary professorial fellow at the University of Melbourne.

Advertisement

The chemical is known to cause cancer in animals, but in humans the exposure "threshold" is unknown, says the World Health Organisation.

"There is no direct evidence acrylamide causes cancer in humans, but food regulators, including FSANZ, agree that we should reduce our exposure," the study's authors say.

They found that cereals and grain-based foods were the main sources of acrylamide in our diets, followed by snacks, condiments, fried potato products and meat.

Surprisingly high levels of the chemical were found in fried beef mince, fresh and fried onions, while pre-packaged olives, chocolate-flavoured energy drinks, grilled asparagus, baked beans and prune juice also rated a mention.

"Beef mince has a high surface area which would allow acrylamide to form if the appropriate precursor chemicals were present," the authors say.

"Similarly, onions have a relatively low sugar content compared to many other starchy vegetables. The results indicate that the cooking method and surface area of the food may be a contributing factor for acrylamide formation."

Also confounding expectations were pizza and coffee, which did not have detectable levels of the chemical. Fresh fruit and vegetables were not tested.

"The formation of acrylamide in raw fruits and vegetables is unlikely," the authors say.

In all tested foods, the acrylamide levels "were generally lower than, or comparable to, those reported in Australian and international studies". However, the authors acknowledge that based on WHO estimates "the acrylamide exposure of Australian consumers is consistent with those considered to be of possible concern to human health".

Dr Ian Musgrave, a senior lecturer in the school of medical sciences at the University of Adelaide, responded to the study's results saying: "Our foods are of international quality and indeed perform better in some aspects compared to international benchmarks.

"There were no perchlorates in water, and the majority of the population is not exposed to levels of aluminium likely to cause health issues.

"The statement that may cause concern is the findings on acrylamide . . . The issue is that while the levels consumed are 50 times lower than the safety threshold, regulators would prefer this to be 500 times lower."

"Taking it easy when it comes to these foods, as regulators advise, has as much to do with overeating and obesity as it has with acrylamide," he says. "It's a tough call, but 'a little of what you fancy' is probably still the way to go."

The results of the second part of the Total Diet Study, yet to be published, will focus on food packaging chemicals.

Correction: It was previously stated that acrylamide is used to treat water. Acrylamide can occur in drinking water as a minor impurity; the result of polyacrylamides which are used in the treatment of water. Acrylamide has not been found in Australian drinking waters.